1. Field of the Invention
The invention relates to a magnetic core having a stack of laminations, in particular wherein the laminations comprise an amorphous metal material. The method for making the laminations and the core containing them, includes stamping the laminations from an amorphous metal sheet using a closely guided high power stamping process, certain heat treatments, and techniques for automated handling using spindles are provided for processing the material into laminated magnetic cores.
2. Prior Art
As shown in FIGS. 1(a) to 1(c), a magnetic core 110 can comprises a stack of laminations 112, cut from strip of ferrous sheet metal 114. The laminations are shaped as required for the application, such as a transformer or inductor. In the example shown in FIGS. 1(a) to 1(c), the core 110 comprises a torus of annular rings, stacked axially.
Each lamination may be stamped from the sheet metal strip 114 in a blanking process. The strip 114 may comprise an electrical steel. Typically the laminations are at least between about 0.006 inch (152.4 μm) and 0.014 inch (355.6 μm) in thickness. Above that thickness, eddy current losses degrade the permeability of a magnetic core 110 containing the stack of laminations. Performance can also be adversely affected by plastic deformation and strains, especially at the inner and outer edges 112a and 112b, respectively, caused by the process of stamping the lamination, which can distort the edge crystal structure during stamping. These strains significantly degrade the magnetic properties of a magnetic core formed from such laminations.
The strip 114 may comprise Ni—Fe, and can vary as to specific composition and metallic structure. Different compositions and structures are characterized by differences in electromagnetic performance. Different compositions are relatively easier or more difficult to stamp in a manner that produces high quality laminations. Annealing after punching can relieve stresses and heal some of the edge deformation, but not eliminate them. It would be preferable if the stamping process could be arranged to avoid stress and deformation, or alternatively, arranged to enable stamping of more demanding material compositions that might improve the electrical performance of the resulting magnetic core.